Phased array transmit/receive systems are an example for RF systems desired for many application such as broadcasting, radar, space communication, weather research, optics, radio frequency (RF) identification systems and tactile feedback systems. Such systems may also be used for gesture sensing, communication backhauling and high speed routing in wireless gigabit (WiGig) or other consumer wireless systems.
A phased array system comprises an array of antennas in which relative phases and amplitudes of a plurality of signals transmitted over the antennas or received via the antennas may be adjusted. This adjustment may be performed in various pails of the systems and devices, for example RF, intermediate frequency (IF) or baseband (BB) parts, before or after analog-to-digital or digital-to-analog conversion etc. By proper adjustment, an effective radiation pattern of the array may be formed in a desired manner, which is also referred to as beamshaping. This beamshaping of the radiation pattern occurs due to constructive and destructive interference between the signals transmitted by each antenna of the array of antennas. Through adjustable phase and amplitude relationships, so-called beamsteering may be performed, i.e. the radiation pattern may be modified also during transmission. Reception may be done in a similar manner, thus providing a reception sensitive to a particular radiation pattern, for example to radiation from a particular direction.
One type of phased arrays is a dynamic phased array. In a dynamic phased array, each signal path providing a signal to an antenna incorporates an adjustable phase shifter, and these adjustable phase shifters may for example collectively be used to move a radiation beam. Moreover, the signal paths may comprise adjustable amplifiers, which provide further adjustment possibilities. Such adjustable phase shifters and/or amplifiers may exhibit variations in the behavior for example due to process variations or temperature variations. This influences the accuracy of a radiation pattern generated or received and/or may influence the accuracy of beamsteering. Generally, for exact beamsteering exact phase relationship between various signal paths are required.
In such phased arrays, reference clock signals or transmission signals are often transmitted to a plurality of individual circuit parts controlling the antennas. Different conductive path lengths to the different circuit parts may result in different phase offsets. However, precisely controlling phase differences between the different antennas is important for the operation of the phased array. Therefore, it is desirable to be able to measure the phase offsets generated by different conductive path lengths, so they can be taken into account for example when controlling adjustable phase shifters.